The Enzymic Synthesis of Amino Acyl Derivatives of Ribonucleic Acid

Non‐canonical Amino Acid Substrates of E. coli Aminoacyl‐tRNA Synthetases

“…A wide variety of straight and branched chain aliphatics are substrates for wild‐type or mutant ValRS ( V1 – V4 ) [44,86,177,178] . The hydrocarbon side chains can also be substituted with cyano groups ( V5 ), azide ( V6 ), hydroxyl groups ( V7 ), a thioether ( V8 ), and ethers ( V9‐V10 ) [25,179] .…”

“…The hydrocarbon side chains can also be substituted with cyano groups ( V5 ), azide ( V6 ), hydroxyl groups ( V7 ), a thioether ( V8 ), and ethers ( V9‐V10 ) [25,179] . Early experiments by Berg and Dieckmann [178] showed that chlorobutyric acid derivatives V11 and V12 are decent substrates; and more recently Easton showed that these interesting AAs could be incorporated into proteins [62] …”

Incorporation of chlorinated analogues of aliphatic amino acids during cell-free protein synthesis

“…It was known already that the chloride 1a is incorporated into proteins 14 and acts as an antagonist of (S)-Val (4) to interfere with haemoglobin biosynthesis, 15 but the efficiency and extent of its incorporation had not been investigated. The V max /K m value for its adenylation by Val-tRNA synthetase (ValRS) of E. coli ML30 is 30% of that of (S)-Val (4), 16 but this is only one step towards protein synthesis. (2S,3R)-Thr 17 and (S)-Abu are also adenylated by the ValRS but they do not even survive transfer to the related Val tRNA in the following step.…”

“…18 Even less information was available about the chloride 1b. Its V max /K m value for adenylation by the ValRS is 1.5% of that of (S)-Val (4) 16 and it is 20% as active as the diastereomer 1a as a Val antagonist against haemoglobin biosynthesis. 15 None of the chlorides 2a,b-3a,b had been studied in this context, although the leucine analogue 2b had been found to have antibacterial activity that is reversed by (S)-Leu (5).…”

“…In this context it is noteworthy that (2S,3R)-Thr is adenylated by the ValRS of E. coli ML30, but (2S,3S)-allo-Thr is not. 16 In this first step of incorporation, an OH group is accommodated in place of one Me substituent of (S)-Val (4) but not the other. The pattern of incorporation of the chlorides 1a,b parallels that for adenylation of (2S,3R)-Thr and (2S,3S)-allo-Thr, with the Cl being preferentially accommodated in place of the Me that may be substituted for OH.…”